1. Field of the Invention
The present invention relates to a method for correcting for distortion of a projected image, a program for correcting image distortion, and a projection-type image display device and more particularly to the method for correcting for the distortion of the projected image caused by projecting an image with a projection optical axis being tilted from normal to the screen, the program for correcting image distortion, and the projection-type image display device to which the above method for correcting for the distortion of the projected image is applied.
The present application claims priority of Japanese Patent Application No. 2002-105613 filed on Apr. 8, 2002, which is hereby incorporated by reference.
2. Description of the Related Art
A projection-type image display device (projector), after having modulated light emitted from a light source using a display device such as a liquid crystal panel or a like, projects the modulated light onto a screen through an optical lens to achieve display of an image. In many cases, the projection-type image display device projects the image onto a screen with a projection optical axis being tilted from normal to the screen rather than with the screen and the projection optical axis being intersected at right angles. In this case, for example, a rectangular image is displayed on the screen as the image having been distorted to be trapezoidal.
Then, in the conventional projection-type image display device, corrections for distortion of projected image caused by projecting the image with the projection optical axis being tilted from normal to the screen are made. Technology of a conventional projection-type image display device as described below is disclosed, for example, in Japanese Patent Application Laid-open No. 2002-6391. That is, in the disclosed conventional projection-type image display device, first, a graphic pattern having a rectangular shape or a like is displayed on a display device being placed independent of an existing screen and, at a same time, the same graphic pattern as above is displayed on the screen. Next, vertices (corrected points) of the graphic pattern having the rectangular shape or a like being displayed on the display device are moved and the resulting graphic pattern having a deformed quadrilateral shape are displayed on the display device and, at this time, deformation ratio parameters of the graphic pattern having the deformed quadrilateral shape to its original graphic pattern are calculated and, at the same time, the graphic pattern having the deformed quadrilateral shape is displayed on the screen. If the graphic pattern having the deformed quadrilateral shape being displayed on the screen is the same as the original graphic pattern, the deformation ratio parameters obtained at that time are stored. Then, an image fed from an outside is converted based on the stored deformation ratio parameters and the converted image is displayed on the screen. The technology employed here is hereinafter called a “first conventional technology”. Moreover, the first conventional technology includes a free setting mode in which an arbitrary correction point can be designated in the image displayed on the screen.
Moreover, technology for another projection-type image display device as described below is disclosed, for example, in Japanese Patent Application Laid-open No. 2002-44571. That is, the disclosed projection-type image display device is provided with a displaying unit to project any of image each having a regularly polygonal as a test image on a screen, an inputting unit to input coordinates of a distortion-free test image corresponding to coordinates of a specified position defining a distortion contour of the image as the test image projected on the screen, a pointing device to move the specified position defining the distortion contour of the image projected as the test image to coordinates of the distortion-free test image input by using the above inputting unit, and a correcting unit to correct for distortion of projected image based on a relation between the coordinates of the specified position defining the distortion contour of the image projected as the test image and the coordinates corresponding to the distortion-free test image. The technology employed here is hereinafter called a “second conventional technology”.
The above first conventional technology is configured based on the premise that, by using an information processing device such as a personal computer or a like, a same image as is to be displayed on a display device making up the information processing device is also projected onto a screen. Therefore, if the above first technology is applied to a case where an image is projected onto a screen singly by a projection-type image display device, a display device is independently required, causing a parts count to be increased. Moreover, in the projection-type image display device employing the second conventional technology, since a pointing device such as a mouse or a like is required, the parts count increases and since a table used to operate the pointing device is also required, the projection-type image display device is limited in its installation place. Furthermore, in the above first and second conventional technologies, direct designation of a position to be corrected by using the pointing device is needed, however, the pointing device itself is constructed based on the premise that an operator manipulates it while seeing a pictorial image being displayed on a display device being put on a same table where the pointing device is being manipulated. Therefore, as in the case of the above first conventional technology, another display has to be placed, independently of a screen and, as in the case of the second conventional technology, the operator has to manipulate the pointing device while seeing an image projected as a test image on a screen being placed apart by several meters. As a result, the first conventional technology has a disadvantage in that a parts count is increased and the second conventional technology also has a disadvantage in that operability of the projection-type image display device is low.